In some orthopedic surgical procedures, such as total knee arthroscopy, surgical instruments generally known as knee distractors have been developed for orienting a patient's knee joint. For example, in a total knee replacement procedure, controlling the relative positions of a patient's tibia and femur during surgery allows a surgeon to set the orientation of the knee joint and obtain predetermined anatomic and mechanical axes along which the knee joint will operate after surgery.
In order to control the relative position of a patient's tibia and femur, a knee distractor may be inserted between the proximal end of the tibia and the distal end of the femur and operated to space the tibia from the femur to set the orientation and joint space of the knee joint. Some knee distractors can be operated to independently space lateral and medial sides of the tibia and femur to obtain a predetermined orientation of the knee joint.
Some distractors may include sensors or scales to measure the joint force of the patient's knee joint during the distraction process. Such distractors are commonly known as ligament balancers. During operation, a ligament balancer may be used to help balance the surrounding soft tissue (i.e., ligaments) of a patient's joint. For example, in a total knee replacement procedure, ligament balancing may be performed to ensure a generally rectangular shaped extension gap and a generally rectangular shaped flexion gap at a predetermined joint force value between the patient's natural or prosthetic proximal tibia and the patient's natural or prosthetic distal femur.
To do so, a ligament balancer may be positioned between a patient's tibia and femur, similar to a standard distractor, to measure the medial and lateral joint forces and the medial and/or lateral gap displacements when the patient's leg is in extension (i.e., the patient's tibia is positioned at about 0 degrees relative to the patient's femur) and in flexion (i.e., the patient's tibia is positioned at about 90 degrees relative to the patient's femur). In either extension or flexion, if the medial and lateral gap displacements are not approximately equal (i.e., do not form a generally rectangular shaped joint gap) at the predetermined joint force value, ligament release may be performed to equalize the medial and/or lateral gap displacements. Sometimes use of a knee distractor and a ligament balancer may be difficult for a surgeon or assistant and may require multiple insertion and removal procedures for each to be used during a single surgery.